A number of known containers (alternatively referred to as dispensers) for a solid block or soft solid mass, such as dispensers in particular, for cosmetic materials or toiletries or other materials for personal or household use, comprise a barrel having one end through which the material can be dispensed, that end being open for dispensing a solid block or closed by an apertured cap for dispensing a soft solid mass. A rotor wheel is mounted at the opposite end of the barrel, and is fixed to a threaded rod which extends axially within the barrel and engages a correspondingly threaded mounting in a follower, a piston located within the barrel. When the rotor wheel is rotated, the threaded rod is likewise rotated and engages with the corresponding threading on the mounting of the piston, thereby translating the rotational movement of the rod into axial movement of the piston.
The transverse cross section of the barrel is at the discretion of the producer, commonly being either round or oval. The rotor wheel has typically comprised a round wheel projecting through opposed windows in a skirt depending from the base of the barrel. An alternative type of rotor wheel, as described in U.S. Pat. No. 3,612,705 and subsequently in EP-A-713660, comprises a wheel having approximately the same transverse cross section as the barrel and mounted underneath the barrel. Such an arrangement is particularly suitable for a non-circular barrel and wheel, for example, an oval barrel and wheel, because rotation of the wheel out of and into alignment with the barrel provides a readily apparent and effective means to meter the solid block or soft solid mass of material out of the dispenser. In U.S. Pat. No. 3,612,705, U.S. Pat. No. 5,868,510 and EP-A-813829 there is also described the location of small round bosses on the top surface of the rotor wheel and complementary shallow sockets indented into the bottom surface of the base of the barrel to align the rotor wheel with the barrel on each turn of the wheel. The present inventors recognise that this has benefits not only during the dispensing operation, but also preventing the wheel and base to become misaligned during transportation of the dispenser before it is filled. However, the design described in U.S. Pat. No. 3,612,705 presents a number of difficulties in practice for its smooth and effective implementation. The barrel is often produced by injection moulding of a thermoplastic, and the gate into the mould is normally located at the bottom of the barrel. The residual excess plastic in the gate forms an irregular protuberance beneath the bottom surface of the barrel which can impair the smooth rotation of rotor wheel. The alignment of a small round boss with a corresponding shallow socket is comparatively difficult because even a small spacial displacement can result in misalignment. Furthermore, when the small round boss on the wheel is rotated into contact with the edge of the bottom of the barrel, the vertical displacement of the wheel from the barrel bottom in order to accommodate the boss must be achieved suddenly due to the sharp profile of the boss. This has a number of effects. Impact of the boss at the same point at the base of the barrel wall can cause damage to the wall or to the boss, and with repeated turnings of the wheel relative to the barrel can result in the boss being worn away, so that it ceases to be effective eventually to perform an alignment function. Because a round boss provides approximately a point contact with the wall of the barrel on rotation, the impact is sudden and the resistance to rotation great, so that wheel rotation encounters a sudden stiffness.
It is an objective of the present invention to mitigate or avoid one or more of the difficulties described hereinabove.